Hi Cosmicgirl and welcome,
In really simple terms, oestrogen is the bleeding hormone. As you’re perimenopausal and your periods were really heavy and closer together, your progesterone levels tanked first. The same happened to me. In an ideal world, our hormones would decrease the same at the same time, but they don’t. 😔
At the beginning of your cycle (day 1 of your period), you have plenty of oestrogen but very little progesterone in your system. Now you have added in more oestrogen your womb is thinking wtf?? and has decided to have a bleed. It’s actually a good thing because it shows it’s working. When you add in the progesterone weeks 3 and 4, you will probably get another, albeit very light bleed at the end. Your body will eventually adjust to the 4 week cycle but it can take a few months for the womb to stop complaining and behave itself.
As for the sore boobs, this is another sign of high oestrogen levels, which would correlate with your oestrogen patches and your own oestrogen levels. Unfortunately during peri menopause our own hormones are fluctuating in the background and HRT can take a bit of time to ‘tame’ them. It will happen though. See how you go with the Evorel sequi. If thing’s haven’t calmed down within a few months, there are other options/strengths etc for you to try.
Good luck.